Integrated circuit (IC) package with a solder receiving area and associated methods

ABSTRACT

A single chip integrated circuit (IC) package includes a die pad, and a spacer ring on the die pad defining a solder receiving area. A solder body is on the die pad within the solder receiving area. An IC die is on the spacer ring and is secured to the die pad by the solder body within the solder receiving area. Encapsulating material surrounds the die pad, spacer ring, and IC die. For a multi-chip IC package, a dam structure is on the die pad and defines multiple solder receiving areas. A respective solder body is on the die pad within a respective solder receiving area. An IC die is within each respective solder receiving area and is held in place by a corresponding solder body. Encapsulating material surrounds the die pad, dam structure, and plurality of IC die.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/567,070, entitled “Integrated Circuit (IC) Package with a SolderReceiving Area and Associated Methods” filed on Dec. 11, 2014, whichapplication is hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of semiconductor packaging,and more particularly, to a die pad with a solder receiving area andrelated methods.

BACKGROUND

Integrated circuits typically include a leadframe and an integratedcircuit (IC) die with encapsulating material surrounding the leadframeand the IC die. The leadframe includes a die pad and a plurality ofpins. Soft solder may be used to attach the IC die to the die pad. Softsolder is used for thermal and electrical conductivity performance,particularly for automotive devices.

A high process temperature is needed to melt the soft solder for IC dieattachment. Soft solder has a tendency to overflow beyond the area ofthe IC die being attached to the leadframe. This is due to the wettingbetween the copper leadframe and the soft solder. Solder overflow mayshort the pins. For a multi-chip integrated circuit, soft solder for asecond IC die may overflow to the soft solder for a first IC die withre-melting when attaching the second IC die.

To prevent solder overflow, the leadframe may be formed with side wallsand v-grooves. A drawback of using a leadframe package with side wallsand v-grooves is that the IC die may not be level when attached to thedie pad. This causes the IC die to be tilted when a thickness of thesoft solder (i.e., bond line) is not uniform across the die pad. Anotherdrawback is movement of the IC die after placement on the soft solderdue to solder flow back effect.

One approach for restricting movement of the soft solder during theheating process is disclosed in U.S. published patent application no.2002/0056894. A die pad includes a plurality of slots that extendthrough the die pad to restrict the soft solder. A restrictive region isdefined by the slots such that the soft solder is restricted within therestrictive region. The IC die is positioned on the restrictive region.The solder paste does not flow into the slots because of the cohesion ofthe soft solder. As a result, the soft solder may not flow and expandduring the heating process.

Another approach for preventing solder overflow from shorting the pinsis disclosed in an article titled “Solder Short Reject Reduction in SoftSolder Die Attach (SSD) Process using Mechanical Solder Shield Design,”by Rashid et al., Applied Mechanics and Material, Vol. 301 (2013), pp127-131. A mechanical solder shield is integrated to the soft solderdispenser die attach machine to prevent the molten solder overflows tothe lead area of the device.

SUMMARY

A single chip integrated circuit (IC) package may comprise a die pad, aspacer ring on the die pad defining a solder receiving area, a solderbody on the die pad within the solder receiving area, and an IC die onthe spacer ring and secured to the die pad by the solder body within thesolder receiving area.

The IC package may further comprise an encapsulating materialsurrounding the die pad, spacer ring, and IC die. A plurality of leadsmay extend outwardly from the encapsulating material and be coupled tothe IC die.

The spacer ring may comprise a material different than the die pad. Thedie pad may comprise an electrically conductive material.

The spacer ring may comprise a dry film solder mask material. The spacerring advantageously supports the IC die, and controls a thickness of thesolder body between the die pad and the IC die. This insures that the ICdie will not be tilted when secured to the die pad. Another advantage ofthe spacer ring is that it reduces movement of the IC die due to solderflow back effect.

The spacer ring may be adhesively secured to the die pad. The IC spacerring may be set inwardly from a periphery of the die pad. The spacerring may also be set inwardly from a periphery of the IC die.

A method for making a single-chip IC package as described abovecomprises positioning a spacer ring on a die pad defining a solderreceiving area, positioning a soft solder deposit on the die pad withinthe solder receiving area, and positioning an IC die on the spacer ringand soft solder deposit. The IC die is secured to the die pad as thesoft solder deposit solidifies within the solder receiving area. Themethod may further comprise surrounding the die pad, spacer ring, and ICdie with an encapsulating material.

Another aspect of the invention is directed to using the dry film soldermask material as a dam structure on a die pad for a multi-chip ICpackage. The multi-chip IC package comprises a die pad, and a damstructure on the die pad defining a plurality of solder receiving areas.There are a plurality of solder bodies, with each solder body on the diepad within a respective solder receiving area. There are a plurality ofIC die, with each IC die within a respective solder receiving area andbeing held in place by a corresponding solder body of the plurality ofsolder bodies.

The multi-chip IC package may further comprise an encapsulating materialsurrounding the die pad, dam structure, and plurality of IC die. Aplurality of leads may extend outwardly from the encapsulating materialand be coupled to the plurality of IC die.

The dam structure may comprise a material different than the die pad.The die pad may comprise an electrically conductive material.

The dam structure may comprise a dry film solder mask material. The damstructure may be configured so that each solder receiving area isisolated from the other solder receiving areas. Each solder receivingarea may be completely surrounded by portions of the dam structure. Inaddition, each IC die within a respective solder receiving area may bespaced away from the dam structure. The dam structure advantageouslyprevents soft solder deposits for anyone of the IC die from overflowingto an adjacent IC die. As the soft solder deposits cool they solidify tothe solder bodies.

The dam structure may be adhesively secured to said die pad. The damstructure may be set inwardly from a periphery of the die pad.

A method for making a multi-chip IC package comprises positioning a damstructure on a die pad defining a plurality of solder receiving areas,and positioning a plurality of soft solder deposits on the die pad, witheach soft solder deposit within a respective solder receiving area. Aplurality of IC die may be positioned on the plurality of soft solderdeposits, with each IC die on a respective soft solder deposit. Each ICdie may be secured to the die pad as the respective soft solder depositsolidifies within a corresponding solder receiving area. The method mayfurther comprise surrounding the die pad, dam structure, and pluralityof IC die with an encapsulating material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of an integrated circuit (IC)package with a spacer ring defining a solder receiving area inaccordance with the present invention;

FIG. 2 is a perspective view of the spacer ring formed separate from thedie pad in accordance with the present invention;

FIG. 3 is a perspective view of the spacer ring on the die pad asillustrated in FIG. 2 defining a solder receiving area;

FIG. 4 is a cross-sectional side view of the spacer ring and die pad asillustrated in FIG. 3 with soft solder in the solder receiving area;

FIG. 5 is a cross-sectional side view of the spacer ring, soft solderand die pad as illustrated in FIG. 4 with the IC die on the spacer ring;

FIG. 6 is a flowchart illustrating a method for making a single-chip ICpackage as illustrated in FIG. 1.

FIG. 7 is a perspective view of a dam structure on a die pad defining aplurality of solder receiving areas in accordance with the presentinvention;

FIG. 8 is a perspective view of the dam structure and die pad asillustrated in FIG. 7 with soft solder in the solder receiving areas.

FIG. 9 is a perspective view of the dam structure and die pad asillustrated in FIG. 8 with IC die within their respective solderreceiving areas.

FIG. 10 is a cross-sectional side view of an integrated circuit (IC)package with the dam structure, die pad and IC die as illustrated inFIG. 9.

FIG. 11 is a flowchart illustrating a method for making a multi-chip ICpackage as illustrated in FIG. 10.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Referring initially to FIG. 1, as integrated circuit (IC) package 20includes a die pad 22, a spacer ring 24 on the die pad defining a solderreceiving area, a solder body 26 on the die pad within the solderreceiving area, and an IC die 28 on the spacer ring and secured to thedie pad by the solder body within the solder receiving area.

Encapsulating materials 30 surrounds the die pad 22, spacer ring 24, andIC die 28. A plurality of leads 32 extend outwardly from theencapsulating material 30. The IC die 28 includes a plurality of bondpads 34, and there is a respective bond wire 36 coupling each of theleads 32 to a corresponding bond pad.

The spacer ring 24 is made of a material different than the material ofthe die pad 22. The die pad 22 is typically made out of an electricallyconductive material, such as copper.

The spacer ring 24 advantageously supports the IC die 28, and controls athickness of the solder body 26 between the die pad 22 and the IC die28. This insures that the IC die 28 will not be tilted when secured tothe die pad 22. Another advantage of the spacer ring 24 is that itreduces movement of the IC die 28 due to solder flow back effect.

The spacer ring 24 is formed separate from the die pad 22, asillustrated in FIG. 2. The spacer ring 24 is formed by cutting orpunching out the desired pattern from a dry film solder mask. An exampledry film solder mask material is AUS410. A thickness of the spacer ring24 may be within a range of 10-70 microns, for example.

The illustrated spacer ring 24 has a rectangular shape. The shape of thespacer ring 24 will vary depending on the particular application. Asurface mount technology (SMT) component placement system, commonlycalled a pick-and-place machine, may be used to transfer the patternedspacer ring 24 to the die pad 22.

The spacer ring 24 is adhesively secured to the die pad 22 by applyingpressure at an elevated temperature, as readily appreciated by thoseskilled in the art. The spacer ring 24 and die pad 22 are thentransferred to an oven for curing. The spacer ring 24 defines a solderbody receiving area 40, as illustrated in FIG. 3.

The spacer ring 24 is set inwardly from a periphery of the die pad 22.Since the height of the spacer ring 24 is known, a predetermined amountof soft solder 44 is placed in the solder receiving area 40 as definedby the spacer ring 24, as illustrated by the cross-sectional side viewin FIG. 4. The soft solder 44 may also be referred to as molten solder.

Even though the soft solder extends in height above a thickness of thespacer ring 24, it is confined within the solder receiving area 40. Thisis because the dry film solder mask material forming the spacer ring 24repels the soft solder. If the spacer ring 24 had been formed out of thesame material as the die pad 22, i.e., copper, then soft solder wouldoverflow the spacer ring due to a wetting effect between the soft solderand the copper. In other words, soft solder is attracted to copper whilebeing repelled by a dry film solder mask material.

The IC die 28 is positioned on the spacer ring 24 and is secured to thedie pad 22 by the soft solder 44 within the solder receiving area 40, asillustrated in FIG. 5. As the soft solder 44 cools down it solidifiesinto the solder body 26.

The spacer ring 24 is set inwardly from a periphery of the IC die 28.There is a small volume of overflow solder 47 on the outside of thespacer ring 24 due to placement of the IC die 28 on the spacer ring butnot enough to cause a short on the pins 32.

Referring now to the flowchart 50 illustrated in FIG. 6, a method formaking a single-chip IC package 20 will be discussed. From the start(Block 52), the method comprises positioning the spacer ring 24 on thedie pad 22 to define a solder receiving area 40 at Block 54. Soft solder44 is positioned on the die pad 22 within the solder receiving area 40at Block 56. An IC die 28 is positioned on the spacer ring 24 and issecured to the die pad 22 as the soft solder solidifies within thesolder receiving area 40 at Block 58. The die pad 28, spacer ring 24,and IC die 28 are surrounded at Block 60 with an encapsulating material.The method ends at Block 62.

Another aspect of the invention is directed to using the dry film soldermask material as a dam structure 124 on a die pad 122 for a multi-chipintegrated circuit (IC) package, as illustrated in FIG. 7. The damstructure 124 defines a plurality of solder receiving areas 140(1),140(2), 140(3) on the die pad 122.

The dam structure 124 is made out of material that is different than thematerial of the die pad 122. The die pad 122 is typically made out of anelectrically conductive material, such as copper.

The dam structure 124 is formed by cutting or punching out the desiredpattern from a dry film solder mask. An example dry film solder maskmaterial is AUS410. A thickness of the dam structure 124 may be within arange of 10-70 microns, for example.

The dam structure 124 is adhesively secured to the die pad 122. This isperformed by applying pressure at an elevated temperature, as readilyappreciated by those skilled in the art. The dam structure 124 and diepad 122 are then transferred to an oven for curing.

The dam structure 124 is configured so that each solder receiving area140(1), 140(2), 140(3) is isolated from the other solder receivingareas. Each solder receiving area 140(1), 140(2), 140(3) is completelysurrounded by portions of the dam structure 124. A periphery of theillustrated dam structure 124 has a rectangular shape, and each solderreceiving area 140(1), 140(2), 140(3) also has a rectangular shape.

A plurality of soft solder deposits 144(1), 144(2), 144(3) are placed inthe plurality of solder receiving areas 140(1), 140(2), 140(3), witheach solder receiving area receiving a respective soft solder deposit,as illustrated in FIG. 8. The dam structure 124 advantageously preventsthe soft solder deposits 144(1), 144(2), 144(3) for anyone of the IC diefrom overflowing to an adjacent IC die.

A plurality of IC die 128(1), 128(2), 128(3) are placed on the softsolder deposits 144(1), 144(2), 144(3), with each IC die within arespective solder receiving area 140(1), 140(2), 140(3), as illustratedin FIG. 9. The soft solder deposits 144(1), 144(2), 144(3) may all bepositioned on the die pad 122 before the IC die 128(1), 128(2), 128(3)are placed thereon. Alternatively, each IC die 128(1), 128(2), 128(3) isplaced on a respective soft solder deposit 144(1), 144(2), 144(3) beforethe next soft solder deposit is positioned on the die pad 122. Each softsolder deposit solidifies to a solder body 126(1), 126(2), 126(3) as itcools so as to secure the respective IC die 128(1), 128(2), 128(3) tothe die pad 122.

The dam structure 124 is set inwardly from a periphery of the die pad122. Each IC die 128(1), 128(2), 128(3) within a respective solderreceiving area 140(1), 140(2), 140(3) is spaced away from the damstructure 124.

Encapsulating material 130 surrounds the die pad 122, dam structure 124,and IC die 128(1), 128(2), 128(3), as illustrated in FIG. 10. Aplurality of leads 132 extend outwardly from the encapsulating material130. Each IC die 128(1), 128(2), 128(3) includes a plurality of bondpads 134, and there is a respective bond wire 136 coupling each of theleads 132 to a corresponding bond pad.

Referring now to the flowchart 150 illustrated in FIG. 11, a method formaking a multi-chip IC package 120 will be discussed. From the start(Block 152), the method comprises positioning the dam structure 124 onthe die pad 122 to define a plurality of solder receiving areas 140(1),140(2), 140(3) at Block 154.

A plurality of soft solder deposits 144(1), 144(2), 144(3) arepositioned on the die pad 122 at Block 156. Each soft solder deposit144(1), 144(2), 144(3) is within a respective solder receiving area140(1), 140(2), 140(3). A plurality of IC die 128(1), 128(2), 128(3) arepositioned on the plurality of soft solder deposits 144(1), 144(2),144(3) at Block 158. Each IC die 128(1), 128(2), 128(3) is on arespective soft solder deposit 144(1), 144(2), 144(3). Each IC die128(1), 128(2), 128(3) is secured to the die pad 122 as the respectivesoft solder deposit solidifies within a corresponding solder receivingarea 140(1), 140(2), 140(3).

The die pad 122, dam structure 124, and IC die 128(1), 128(2), 128(3)are surrounded at Block 160 with an encapsulating material. The methodends at Block 162.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

What is claimed is:
 1. An integrated circuit (IC) package comprising: adie pad of a lead frame; a dam structure disposed over the die pad andcomprising a plurality of openings extending through the dam structureto the die pad, the plurality of openings comprising a plurality ofsolder receiving areas, wherein the dam structure comprises a materialdifferent than the die pad; a plurality of solder bodies comprising asolder material, wherein each of the plurality of solder receiving areascomprise a solder body of the plurality of solder bodies; a plurality ofIC dies, each of the plurality of IC dies being attached to one of theplurality of solder receiving areas through a corresponding solder bodyof the plurality of solder bodies; and an encapsulating materialsurrounding the die pad, the dam structure, and the plurality of ICdies.
 2. The IC package according to claim 1, further comprising: amajor surface of each of the plurality of IC dies comprising a bond pad;and a lead of the lead frame disposed within the encapsulating materialand extending out of the encapsulating material, the lead being coupledto the bond pad.
 3. The IC package according to claim 1, wherein the damstructure comprises a dry film solder mask material.
 4. The IC packageaccording to claim 1, wherein the dam structure comprises anelectrically conductive material.
 5. The IC package according to claim1, wherein the dam structure is configured so that each solder receivingarea is isolated from the other solder receiving areas.
 6. The ICpackage according to claim 1, wherein each solder receiving area iscompletely surrounded by portions of the dam structure.
 7. The ICpackage according to claim 1, wherein a periphery of the dam structurehas a rectangular shape, and with each of the solder receiving areasalso having a rectangular shape.
 8. The IC package according to claim 1,wherein the dam structure is adhesively secured to the die pad.
 9. TheIC package according to claim 1, wherein the dam structure is setinwardly from a periphery of the die pad.
 10. The IC package accordingto claim 1, wherein each of the plurality of IC dies within a respectiveone of the plurality of solder receiving areas is spaced away from thedam structure.
 11. The IC package according to claim 1, furthercomprising a plurality of leads extending outwardly from theencapsulating material and coupled to the plurality of IC dies.
 12. TheIC package according to claim 11, wherein each IC die of the pluralityof IC dies comprises: a plurality of bond pads; and a plurality of bondwires, wherein a respective bond wire of the plurality of bond wirescouples each of the plurality of leads to a corresponding bond pad ofthe plurality of bond pads.
 13. An integrated circuit (IC) packagecomprising: a rectangular die pad; a dam structure disposed over therectangular die pad, the dam structure comprising a plurality ofrectangular solder receiving areas, wherein a periphery of the damstructure comprises a rectangular shape, and the dam structure comprisesa dry film solder mask material; a plurality of solder bodies, each ofthe solder bodies being disposed over the die pad within a respectiverectangular solder receiving area; a plurality of IC dies, each of theplurality of IC dies disposed within the respective rectangular solderreceiving area and being held in place by a corresponding solder body ofthe plurality of solder bodies; and an encapsulating materialsurrounding the rectangular die pad, the rectangular dam structure, andthe plurality of IC dies.
 14. The IC package according to claim 13,wherein the dam structure comprises a continuous interior wallcompletely surrounding each of the plurality of rectangular solderreceiving areas from all sides.
 15. The IC package according to claim13, wherein the dam structure comprises an electrically conductivematerial.
 16. The IC package according to claim 13, wherein the damstructure is configured so that each of the plurality of rectangularsolder receiving areas is isolated from the other rectangular solderreceiving areas.
 17. The IC package according to claim 16, wherein thedam structure is adhesively secured to the rectangular die pad.
 18. TheIC package according to claim 16, wherein the dam structure is setinwardly from a periphery of the rectangular die pad.
 19. The IC packageaccording to claim 16, wherein each of the plurality of IC dies isspaced away from sidewalls of the dam structure.
 20. An integratedcircuit (IC) package comprising: a rectangular die pad; a dam structuredisposed over the rectangular die pad, the dam structure comprising afirst rectangular solder receiving area and a second rectangular solderreceiving area, wherein a periphery of the dam structure comprises arectangular shape; a first solder body and a second solder body, thefirst and the second solder bodies being disposed over the die padwithin the first and the second rectangular solder receiving areasrespectively; a first and a second IC die disposed within the first andthe second rectangular solder receiving areas respectively, the first ICdie being held in place by the first solder body and the second IC diebeing held in place by the second solder body; a first bond wire coupledto a first bond pad at a first major surface of the first IC die facingaway from the die pad; a second bond wire coupled to a second bond padat a second major surface of the second IC die facing away from the diepad; and an encapsulating material disposed around the rectangular diepad, the dam structure, and the first and the second IC dies, and thedam structure comprises a different material than the encapsulationmaterial.
 21. The IC package according to claim 20, wherein the damstructure comprises a continuous interior wall completely surroundingthe first and the second rectangular solder receiving areas from allsides.
 22. The IC package according to claim 21, wherein the first andthe second IC dies are spaced away from the continuous interior wall.23. The IC package according to claim 20, wherein the dam structurecomprises an electrically conductive material.
 24. The IC packageaccording to claim 20, wherein the first rectangular solder receivingarea is isolated from the second rectangular solder receiving area. 25.The IC package according to claim 20, wherein the dam structure isadhesively secured to the rectangular die pad.
 26. The IC packageaccording to claim 20, wherein the dam structure is spaced from aperipheral edge of the rectangular die pad.